Vray5 / PhoenixFD not using all cores while rendering

[waaazoo]

Hi,

I'm trying to render stills on a Vray5 scene with PhoenixFD ocean + foam and splashes. Resolution is at 5000 pix wide and I'm rendering on a 64core Threadripper with 256Gb Ram.
The file renders, but is not using all cores. I tried with progressive and bucket rendering (still trying). One of my tests starting with 100% CPU use at rendering (bucket), but then dropped to less than 50% use.
I tried also with FD4.40.00, FD4.41.00, Vray5 update 1, Vray 5 update 1.1.... all on Maya 2019.3.1
I will try with Maya 2020 also. I'm mayabatch (command line) rendering.
I will also try distributed within Maya to see if makes any change.

Is it a known issue ?

[georgi.zhekov]

Hey,

Could it be that you're at a point where V-Ray is still compiling the geometry (displacement, etc.) but not started rendering?

Does the CPU load go to 100% at some point or stays low till the render completes?

While preparing the render - collecting textures, building geometry, displacement - it is expected that the utilization will not be at 100%, but once the render starts and the buckets show up it should go to 100%.

If you start mayabatch from the command line in the log there should be a message in the lines of "V-Ray: Rendering image... " - at this point you should get full utilization.

[waaazoo]

Hey,

Could it be that you're at a point where V-Ray is still compiling the geometry (displacement, etc.) but not started rendering?

Does the CPU load go to 100% at some point or stays low till the render completes?

While preparing the render - collecting textures, building geometry, displacement - it is expected that the utilization will not be at 100%, but once the render starts and the buckets show up it should go to 100%.

If you start mayabatch from the command line in the log there should be a message in the lines of "V-Ray: Rendering image... " - at this point you should get full utilization.

Hi Georgi,

Thanks for your answer.
Compiling ends and render starts, for sure. Curiously, when render starts ("V-Ray: Rendering image... "), it starts at full load, and after 10% of the render is completed it drops progressively up to 35%.
I am aware that preparing render, collecting, compiling, etc. is not at full load.
I have no error messages during preparation. It loads the AUR, the HDR and all the textures.

I am trying now to build up a fresh scene in maya 2020 to see if it's related to the scene I had.

[georgi.zhekov]

Please let us know how it goes and if you have a scene that you think is not behaving properly, send it over and we will take a look.

Thanks!

[waaazoo]

Okay, I made a bunch of new tests. First, I built up a new scene in Maya 2020.1. Then I made a fresh install on the 64 core node (Maya 2020.1, Vray 5.10.20, PhoenixFD 4.41.00)

Test1: 2500 pix wide (Sea, Foam, Splash, Boat)
CPU: Compiling from 2% -> 56%
Building embree 100%
Render start at 100% and dropping down to 50%

Test2: 2500 pix wide (Sea, NoFoam, NoSplash, Boat)
CPU: Compiling from 2% -> 56%
building embree 100%
Render start from 100% up to the end

Test3: 2500pix wide (Sea, Foam, NoSplash, Boat)
CPU: Compiling from 2% -> 56%
Building embree 100%
Render start at 60% and dropping down to 36% -> up again to 50% (I didn't let it finish)

Test4: 2500pix wide (Sea, NoFoam, Splash, Boat)
CPU: Compiling from 2% -> 48%
Building embree 100%
Render start at 100% and dropping down to 70%, then 42%, then 38% (I didn't let it finish)

Test5: 2500pix wide (Sea, Foam, Splash, Boat) No Motion Blur on Foam and splashes
CPU: Compiling from 2% -> 51%
Building embree 100%
Render start at 50% and dropping down to 36% (I didn't let it finish)

Test6: 2500pix wide (Sea, Foam, Splash, Boat) Point Mode for Splash and Foam (all previous were with cellular (foam) and splashes (splash)
CPU: Compiling from 2% -> 52%
Building embree 100%
Render start at 100% -> 60% -> 80% -> 90% -> 99% (render completed at 10%)-> 60% (render complete at 20%)-> 99% up to end

Test7: 2500pix wide (Sea, Foam, Splash, NoBoat) Again with cellular (foam) and splashes (splash) - Bucket 32 (like all previous)
CPU: Compiling from 2% -> 51%
Building embree 100%
Render start at 50% and dropping down to 36% (I didn't let it finish)

Test8: 2500pix wide (Sea, Foam, Splash, NoBoat) Again with cellular (foam) and splashes (splash) - Bucket 8
CPU: Compiling from 2% -> 51%
Building embree 100%
Render start at 33% ... (I didn't let it finish)

Test9: 2500pix wide (Sea, Foam, Splash, NoBoat) Again with cellular (foam) and splashes (splash) - Bucket 128
CPU: Compiling from 2% -> 51%
Building embree 100%
Render start at 70% then dropping down to 45% (I didn't let it finish)

Test10: 2500pix wide (Sea, Foam, Splash, NoBoat) Again with cellular (foam) and splashes (splash) - Progressive
CPU: Compiling from 2% -> 51%
Building embree 100%
Render start at 100% then dropping down at 40% (I didn't let it finish)


So... only thing which is sure is that CPU utilization has to do with particle system of PhoenixFD. All other tests have a similar pattern of behaviour.
I will send the scene to support, without the boat. All my test renders were done at frame 1041 and camera1, and I will send the corresponding AUR file.
I'm curious to know if I have any bad setting here.

[waaazoo]

Last but not least...

I did a DR test launched from the 16 core workstation with the 64 core as slave (from Maya interface). I can confirm that there are 32 buckets for master (CPU at 96% average) and 128 buckets for slave (CPU 38% average) ! Damn !

[EDIT] File was sent, ticket number: 1241

[georgi.zhekov]

Thanks a lot for the scene. Got it.

We will let you know when we find what is going on.

[waaazoo]

Thank you Georgi ! I'm really curious to see if this issue can be quickly resolved.

[georgi.zhekov]

Looks like you hit an issue that is already logged in our bug-tracking system. Using bubbles,splashes or celluar mode in the Particle Shader will not utilize the CPU well on high-core count machines.

Until we fix it as a workaround you can use the point or the fog mode in the Particle shader (just make sure to turn off the Volume Light Cache checkbox in the Particle shader options as this might impact the CPU utilization as well).

Hope this helps. We will update the thread once we have a fix.

[waaazoo]

Hmmm, how sad. Thanks for the answer. I will try to use point mode (without volume light cache), but usually this doesn't look as good as bubbles/cellular/splashes. I hope this can be resolved in near future.

[waaazoo]

At least I can confirm that using point mode without particle light cache resolves the issue with CPU usage. I'm trying to get a satisfying result now. Thanks.

[waaazoo]

Now I get a new problem. Render crashes at 5000pix wide because of Embree raycaster. As far as I know, there is no way to disable Embree anymore.



I have to say that since Vray5 It happens very often to loose a big amount of time just trying to get around problems. It starts to be annoying not being able to do this or that because it doesn't work. I'm quite disappointed. No bashing here. I only would like to do my job which is design and rendering.

[georgi.zhekov]

Hmm, is this the same scene that you sent?
Is this happening only when you render at such resolution, does it work with lower res?

[waaazoo]

Yes, same scene but with the boat (not too heavy). Yes, it renders now at 4000pix wide, but won't render at 5000 pix wide. And it's not a RAM issue as I have 256Gb.

[EDIT] same scene but with point mode on foam and splashes

[Paul Oblomov]

What if you disable those infinite primitives? I suppose, it is phx ocean. It heavy relies imo on static. If it works without ocean - try to play with ocean mesh settings. In the end, you can export it to mesh and render. Not that oneclick solution, but you can finish ur job.